Electrical restraining device for free-piston units



Mmh 21, wsw v. GRONSTEDT ETAL 295493943343 ELECTRICAL RESTRAINING DEVICEFOR FREE-PISTON UNITS Filed Aug. 25, 1944 2 Sheet-Sheet 1 FEG. i

March 2E, 19% v. CRONSTEDT ETAL 295m@3@ ELECTRICAL RESTRAINING DEVICEFOR FREE-PISTON UNITS Filed Aug. 23, 1944 2 Sheets-Sheet 2 Patented Mar.2i, 19 fit Val Cronstedt, Marlboro, William Howard Sprenkle, Andover,and Andrew Kalitinsky, Eagleville, Conn., assignors to United AircraftCorporation, East Hartford, Conn., a corporation of Delaware ApplicationAugust 23, 1944, Serial No. 550,878 8 Claims. (Cl. 230-56) Thisinvention relates to an electrical restraining linkage by which theopposed pistons of a free-piston unit may be caused to movesymmetrically.

The opposed pistons have been maintained always at equal distances fromthe center of the engine by an interconnecting restraining linkage whichhave been, in'general, of two types. One type has a rocking lever withthe ends connected by rods to the pistons, and the other has anoscillating pinion engaging with racks on a pair of rods extending fromthe pistons. A feature of this invention is an electrical restrainingdevice which requires no mechanical connection between the pistons.

Another feature is a device by which changes in an electrical circuitmay result from the movement of one of the pistons or from -a change inthe position of the piston. Another feature is an electrical device forcontrolling or changing one or more of the operating conditions of theunit, such as a change in the pressure in the air spring.

Another feature is the electrical control of one or more of theoperating conditions afiecting the unit, for causing the opposed pistonsto move symmetrically. This control may affect only one of the pistons.

Other objects and advantages will begapparent from the specification andclaims and from the accompanying drawing which illustrates what is nowconsidered to be a preferred embodiment of the invention.

Fig. l is a sectional view through the freepistonengine-and-compressorunit.

Fig. 2 is a diagrammatic view of the electrical system.

The unit shown includes an engine cylinder I having reciprocatingpistons l2 and I4 to which compressor pistons l6 and IS in cylinders 20and 22 are integrally connected. Sleeves 24 and 26 attached to thecompressor pistons complete the reciprocating piston assemblies. Thesleeves in combination with stationary pistons 28 and 30 form air springcylinders.

The piston assemblies are moved apart by the burning of fuel injectedinto engine cylinder l0.

Air compressed in the air spring cylinders on the power stroke returnsthe piston assemblies.

Intake manifold 34 conducts air to intake valves 36 through which airalternately enters opposite ends of the compressor cylinders. Thecompressed air leaves the cylinders through discharge valves 38, also atopposite ends of the compressor cylinders, and passes through scavengemanifold 40 and through ports 42 and 44 which are 'un covered by pistonsl2 and I4 at the end of the power stroke, thereby permitting air to beblown through the engine cylinder and exhaust ports 46 and 48 intoexhaust manifolds 60.

The pistons are maintained at equal distances from the center of theengine cylinder by the electrically operated device, showndiagrammatically in Fig. 2, which causes the pistons to movesymmetrically. The device may include a pair of rods 52 and 54 extendingfrom pistons i6 and ill (see also Fig. l) and carrying permanent magnetsor cores 56 and 58, moving in solenoids 60 and 62 in a housing 64,Fig. 1. These solenoids are in opposition to each other in a closedcircuit 65 which also has coils 66 and 68 in series. These coils are ina position to act on a magnetic bar Ill.

While the pistons move symmetrically, magnets 56 and 58 also movesymmetricallv within solenoids 60 and 62 and equal power is induced inthe solenoids. As a result, no power is supplied to the coils 66 and 68so that bar Ill remains in the position shown. However. if either pistontends to move out of symmetry, the power induced in one of the coils 60and 62 will overbalance the other and current will flow through coils 66and 68, causing bar I0 to move. The circuit is arranged in such a mannerthat bar 10 will move in one direction if piston I 8 moves more rapidlythan piston l6 and in the opposite direction if the reverse is true.

Bar Hi forms a part of each of two parallel circuits 12 and 14, bothincluding a source of power which may be a battery it. Circuit 12includes a coil 18 surrounding a core 80 to which is connected a valve,not shown, in air spring piston 28. Similarly, circuit it includes acoil 84 surrounding a core 86 connected to a valve 88 in the air springpiston 36. Valves connect the air springs to the atmosphere.

Bar 10 carries spaced contacts 90 and 92 enaging alternately with fixedcontacts 94 and 96 in circuits l2 and 14 respectively for completing thecircuits.

Gas under pressure is supplied to the air sprin s from chambers 98 andI00 surrounding pistons 2n and 30 and communicating through openings M2in sleeves 24 and 26, with the space within the sleeves. These openingsare arranged to be uncovered when the piston assemblies approach theinner ends of the strokes. Gas may be supplied to chambers 98 and I0!)through conduits I04 and I06 to maintain similar pressures in bothchambers.

In operation, if piston l8 moves inwardly more rapidly than piston IS,the electromotive force in coil 62 becomes greater than that of coil 60and moves bar 10 to close circuit 14, thereby opening valve 88momentarily to reduce the pressure in the air spring acting on pistonl8. As a result, the pistons will not move measurably out of symmetry.Similarly, if piston l6 approaches nearer the center than piston I8,circuit I2 will be closed to reduce the pressure in the 'air springacting on piston ll.

Either solenoid 60 or 62, in conjunction with the core movable therein,constitutes an electrical device in a circuit, the power in which ischanged by the movement of the piston. The change in the power of thiscircuit, by closing either circuit I2 or 14, changes one of theoperating conditions affecting the movement of one of the pistons andthus controls the piston movement.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

We claim:

1. A free-piston unit having a cylinder, opposed engine pistons in thecylinder, air springs acting on the pistons for moving said pistonstoward each other, said pistons being moved apart by combustion of fuelin the cylinder, an electrical circuit, means responsive to anonsymmetrical movement of the pistons for procuring a change in theelectrical circuit, and means controlled by the change in the circuitfor adjusting the pressure of the air in one of said springs.

2. In a restraining mechanism for the opposed engine pistons in theengine cylinder of a free-piston unit, said pistons being moved apartcircuit for adjusting the effective force oi. one of the air springs.

6. In a free-piston engine-and-compressor unit, an engine cylinder,opposed engine pistons in said cylinder, said pistons being moved apartby the combustion of fuel in the engine cylinder,

air springs acting on the pistons for moving said pistons toward eachother, a compressor piston connected to each of said engine pistons, acompressor cylinder in which each compressor piston reciprocates, thefrequency of the cycle oi? each piston being changed by variations inoperating conditions including air spring pressure, compressor inletpressure, compressor discharge pressure, and effective length of thecompressor piston stroke, and electrical means responsive to anon-symmetrical movement of the pistons for adjusting one of saidoperating conditions affecting one of the pistons.

7. In a free-piston engine-and-compressor unit, an engine cylinder,opposed engine pistons in said cylinder, said pistons being moved apartby the combustion of fuel in the engine cylinder,

air springs acting on the pistons for moving said pistons toward eachother, a compressor piston connected to each of said engine pistons, acompressor cylinder in which each compressor pisby the combustion orfuel in the engine cylinder and being moved together by air springsacting on the opposed pistons, said pistons normally movingsymmetrically with respect to the center of the engine cylinder,electrical means connected to said pistons and responsive to anonsymmetrical movement of the pistons for adjusting the pressure in oneof said air springs.

3. In a restraining mechanism for the opposed engine pistons in theengine cylinder of a free-piston unit, said pistons being moved apart bythe combustion of fuel in the engine cylinder and being moved togetherby air springs acting on the opposed pistons, said pistons normallymoving symmetrically with respect to the center of the engine cylinder,electrical means connected to said pistons and responsive to anonsymmetrical movement of the pistons for changing the effective forceof at least one of the air springs.

4. In a free-piston engine-and-compres'sor unit, an engine cylinder,opposed engine pistons in said cylinder, said pistons being moved apartby the combustion of fuel in the engine cylinder, air springs acting onthe pistons for moving said pistons toward each other, a pair ofelectrical means, one of which is associated with each piston, a pair ofsimilar circuits, each including one of said electrical means, each ofsaid means operating in response to reciprocation of the pistons forprocuring changes in the electrical circult, and means controlled by anunbalance in the changes in the circuits for adjusting the eifectiveforce of one of said air springs.

5. In a tree-piston engine-and-compressor unit, an engine cylinder,opposed engine pistons in said cylinder, said pistons being moved apartby the combustion of fuel in the engine cylinder, air springs acting onthe pistons for moving said pistons toward each other, a pair ofsolenoids, the cores of which are connected to the pistons, a circuitincluding the solenoids in opposition, and means contro led by anunbalance in the ton reciprocates, the frequency of the cycle of eachpiston being changed by variations in operating conditions including airspring pressure, compressor inlet pressure, compressor dischargepressure, and effective length of the compressor piston stroke, a pairof solenoids, the cores of which are connected to the pistons, a circuitincluding the solenoids in opposition, and means controlled by anunbalance in the circuit for adjusting one of said operating conditionsaffecting, one of the pistons.

8. In a free-piston engine-and-compressor unit, an engine cylinder,opposed engine pistons in said cylinder, said pistons being moved apartby the combustion of fuel in the engine cylinder, air springs acting onthe pistons for movin said pistons toward each other, a compressorpiston connected to each of said engine pistons, a compressor cylinderin which each compressor piston reciprocates, the frequency of the cycleof each piston being changed by variations in operating conditionsincluding air spring pressure, compressor inlet pressure, compressordischarge pressure, and effective length of the compressor pistonstroke, a pair of solenoids, the cores of which are connected to thepistons, a circuit including the solenoids in opposition, and meanscontrolled by an unbalance in the circuit for adjusting the effectiveforce of one of said air springs.

VAL CRONS'I'EDT. WILLIAM HOWARD SPRENKLE. ANDREW KALITINSKY.

REFERENCES CITED The following references are of record in the file ofthis patent:

